What is happening with the airplane just before you touch down?

If the plane just flys normally down to the ground and bounces, you are too fast. If you are coming in nose-high or level, then flairing and still bouncing, you are just a bit too fast, but it might just be potholes in the runway or landing gear setup.

But, if the nose drops a bit before touchdown, causing the nosewheel to touch first even while you are holding elevator, you are too slow, you just stalled and "pancaked" it.

It's most likely that you are too fast, it's the most common. Lots of good advice above.

As a side note, the throttle position to land will be lower than what is required to move the plane on the ground, espeically if you have a grass runway. Even on pavement, the friction in the wheels and such is enough to keep the plane from moving at a throttle setting that is plenty high for a landing approach.